U.S. Pat. No. 3,894,209 to Fairbairn discloses a nozzle for an energy beam system. This nozzle utilizes a hollow radio frequency electrode housed in an inner sleeve that is telescopically mounted within an outer sleeve. One or more powders or aggregates are selectively fed axially through a bore in this hollow electrode while a gas is selectively fed through the space around the electrode.
U.S. Pat. No. 4,142,089 to Lau et al is directed to a pulsed coaxial thermal plasma sprayer comprising an elongated conductive tube having an electrode position coaxially therein. Inert gas, such as helium, is mixed with a powdered material, such as a ceramic or a metal, and a controlled amount is injected evenly into the tube.
U.S. Pat. No. 4,650,953 to Eger et al describes a plasma torch having an electrode secured to a liquid cooled electrode holder and formed with a flow passage communicating with a central outlet for delivering an ionizable gas. A nozzle body which surrounds the electrode serves to conduct gas along the outside surface of this electrode.